By protraction, I assume that you mean shifting (rotating) the shoulder girdle anteriorly, which involves moving the scalula away from the spine (such as is requires when reaching forward). This motion requires movement at the sternoclavicular, acromioclavicular, and coracoclavicular joints, and is performed by actions of the serratus anterior, pectoralis minor and pectoralis major.
The opposite movement, retraction, is backward movement of the shoulder girdle, and involves moving the scapula back toward the spine. Trapezius (middle and lower fibers), rhomboids and latissimus dorsiare responsible for retraction.
Rhomboideus major and rhomboideus minor inserted at the medial border of the scapula, supplied by dorsal scapular nerve (c5) retracts and elevates the scapula. these are also called as tha brassiers of the scapula.
pectoralis, serratus anterior
Pectoralis minor and serratus anterior
serratus Anterior
Pectoralis minor
serratus anterior
Rhomboids Major and Minor are the primary muscles that Adduct the Scapula.
The functions of a fixator muscle is the stabalizing of the orgin of the prime mover so that the prime mover can act more efficiently. Fixators steady the proximal end of a limb while movements occurs at the distal end. EX: The scapula is a freely movable bone that serves as the orgin for several muscles that move the arm. When the arm contracts the scapula must be held steady.
A prime mover is the muscle that has the most influence in one direction on the joint it acts on. For example the prime mover in extension of the forearm is the triceps.
The primary movement is called the Prime mover or Agonist
The movement of the scapula is largely determined by the position of the shoulder girdle as a whole. As a "floating bone" the scapula is often at the mercy of the more fixed extremities and can be acted upon by several different muscles simultaneously. That being said, the prime mover responsible for scapular depression is the trapezius (specifically the lower fibers). Other muscles which act as stabilizers or synergists in scapular depression and eventual scapular protraction are the subscapularis, the serratus anterior and the lower fibers of latissimus dorsi.
your rectus abdominis is the prime mover in a crunch exercise or spinal flexion
quadriceps
Legs, traps & forearms
biceps brachii
Synergists as well as fixator muscles.
In the canine: the gluteal muscles (superficial, middle, deep).